System for controlling refrigerant condensing pressures by dynamic hydraulic balance



June 25, 1968 w v. MAUER SYSTEM FOR CONTROLLING REFRIGERANT CONDENSING PRESSURES BY DYNAMIC HYDRAULIC BALANCE Filed Nov. 14, 1966 FRO/1 C NDENSER CONDENSER INVENTOR William 1 Nauer United States Patent 0 3,389,576 SYSTEM FOR CONTROLLING REFRIGERANT CONDENSING PRESSURES BY DYNAMIC HYDRAULIC BALANCE William V. Mailer, 7 E. 14th St, New York, N.Y. 10003 Filed Nov. 14, 1966, Ser. No. 593,886 10 Claims. (Cl. 62-196) ABSTRACT OF THE DISCLOSURE A condensing-pressure control system for air cooled and similar condensers wherein the amount of condenser surface required to maintain constant minimum pressure is automatically provided by flooding the unneeded condenser surface with liquid reverse-flow supplied from the receiver; no check or other control valves are required in the condenser-receiver pipe line; the condensed liquid may optionally be partially or fully reheated. Control, being by dynamic hydraulic balance, is virtually instantaneous.

This invention concerns improved control means for refrigerant condensing pressures in refrigeration and air conditioning systems particularly when the condensers are operated at low ambient temperatures.

In refrigeration and air conditioning systems having aircooled condensers, evaporative condensers or atmospheric condensers, the condensers are generally located out-ofdoors or in such locations that they can be cooled by outdoor air. When the ambient air falls in temperature, such low condensing pressures result that there is insufiicient refrigerant pressure to operate properly an expansion valve at refrigerant evaporator located in the cooling chamber of the system. This problem is well known and many expedients have been proposed for solving it. Due to their complexity, insufiicient responsiveness to rapidly changing temperatures, or other factors, the prior expedients proposed have not been wholly satisfactory and trouble-free. The system described in my prior patent, No. 3,248,895, was directed at overcoming the difficulties and disadvantages of prior devices and systems in order to maintain operation of a refrigeration system at high efficiency at all ambient temperatures from sub-zero to more than 100 F., to which an air cooled condenser may be subjected. In that system there was employed one or more valve controlled accumulators together with a valve controlled purge line and a valve controlled pressurizer line for the accumulator. The accumulator operates cyclically to pass refrigerant from the air cooled condenser to the liquid receiver.

In the present invention, the desirable results obtained by my prior system are obtained in a novel, improved and simplified way without using any accumulator, accessory lines to the accumulator and associated valves. The present system employs a valve controlled restricted equalizer line connected between a compressor and the receiver to drive refrigerant at predetermined pressure to an evaporator. In order to effect instant reheating of liquid in the receiver and to mix oil and liquid refrigerant which tend to separate in the receiver, the equalizer line can be extended below the surface of liquid in the receiver and terminated in a hot gas distributor tube assembly.

It is therefore one object of the invention to provide a refrigeration system having an air cooled condenser with 3,389,576 Patented June 25, 1968 ice a direct connection between a liquid receiver and the condenser for matching the condenser capacity to refrigeration load and other variable conditions.

A further object is to provide a refrigeration system as described, wtih an equalizer line connected between a compressor and the receiver, the equalizer line having a differential pressure controlled valve to pass compressed gaseous refrigerant to the receiver when a predetermined pressure difference exists between the pressure in the receiver and the pressure in a high pressure line leading from the compressor to the condenser.

Another object is to provide a refrigeration system as described, wherein the equalizer line terminates in a distributor tube below the surface of liquid in the receiver to effect flash reheating and to keep oil and liquid refrigerant in a mixed condition.

Other objects are: to keep a constant supply of liquid refrigerant under adequate pressure fed to a liquid receiver at all temperatures of ambient air used to cool a condenser; to operate an air cooled condenser at maximum efficiency at all times; to insure instant supply of liquid refrigerant to an evaporator when the system is turned on; to insure constant supply of liquid refrigerant at proper pressure to the evaporator at all times; to effect flash heating of liquid refrigerant at the gas-to-liquid interface in the receiver; to provide an automatically operating control means employing a minimum of moving parts for a refrigeration system.

For further comprehension of the invention and of the objects and advantages thereof, reference will be had to the following description and accompanying drawings and to the appended claims in which the various novel features of the invention are more particularly set forth.

In the accompanying drawings forming a material part of this disclosure:

FIGURE 1 is a diagram of a refrigeration system embodying the invention.

FIG. 2 is a diagram similar to a part of FIG. 1, illustrating another form of the invention.

Referring first to FIG. 1, there is shown a refrigeration system S1 including a compressor 10 which compresses a vapor refrigerant and supplies the same: from its outlet via a high pressure pipe 12 to the inlet of a condenser 14 at the top of the condenser. The condenser is located in ambient air at an outdoor location, in unheated space or in a location where outdoor air can be supplied thereto for cooling the same, or in other gas atmosphere. A fan 16 driven by a motor 18 may be used to drive or draw air across the condenser to cool and condense the hot compressed gas therein. The cooled refrigerant in liquid form but still under pressure is supplied to a liquid receiver 20 via a liquid conducting pipe line or conduit 22. This conduit is unobstructed at all times. The receiver 20 is a closed container containing refrigerant liquid R with a vapor space S above the surface S of the liquid in the re ceiver. Pipe 22 is connected to the receiver at the bottom of the body of liquid R.

The liquid refrigerant R under pressure is fed from an outlet of the receiver through a pipe 26 connected to the inlet end of an evaporator 28, via an expansion valve 30 or equivalent metering device. The evaporator 28 is located in a room, cabinet or other enclosed cooling chamber 32. The liquid refrigerant vaporized by heat drawn from chamber 32 is fed from the outlet of the evaporator via a low pressure or suction line 34 to the inlet or intake of compressor 10.

A pressure responsive regulating valve 36 is connected in the pipe line 12 feeding compressed gaseous refrigerant via supply line 12a to the condenser 14.

Valve 36 is a spring-loaded normally closed valve selected to have an opening point which is adjustable within a range of saturated pressures depending on the particular refrigerant being used. Valve 36 opens when the compressor operates to apply full operating pressure to the condenser. Valve 36 also acts as a check valve to prevent reverse flow of gases from the condenser 14 to the compressor 10 during otfcycle hot weather conditions. Valve 36 further functions to prevent off-cycle flow of refrigerant from the evaporator 28 through the non-operating compressor to the condenser 14 when the temperature of the condenser falls below the temperature inside chamber 32 enclosing the evaporator.

An equalizing pipe line 38 is connected between the high pressure line 12 at the intake end of valve 36, and the top of receiver 20 to apply pressure on the surface S of liquid refrigerant R in the closed receiver. Connected in pipe line 38 is a normally open differential pressure (D.P.) valve 39. This valve is located between equalizer pipe line sections 38, 38". Valve 39 is set to close when the pressure in line 12 rises to a predetermined point below the closing point of valve 36. For example, if valve 36 is set to open when the pressure in line 12 is in the range of 220223 pounds per square inch for a given type of refrigerant the valve 3? may be set to close at a pressure of at least 210 pounds per square inch in pipe line section 38 located between line 12 and the valve.

A thermostatically controlled switch 80 locate-d in cooling chamber 32 is connected in parallel with manually operable switch 77. Both switches are connected in power supply line 81 leading from power supply 50 to compressor 10. Branch line 82 is connected from line 81 to fan motor 18 via a thermostatically controlled switch 33 lo cated outdoors near the condenser 14. Thermostat 8i closes to start compressor 10 when the temperature in cooling chamber 32 rises to a predetermined point. Thermostat 83 closes when the ambient temperature rises above a certain point. Thus the fan will be driven only when the ambient temperature is high enough and when the compressor is operating.

In operation of system S1, the compressor 10 starts either upon the closing of switch 77 manually or in response to closing of thermostat 80 in the cooling chamber 32 which now requires additional cooling. The refrigerant vapor in evaporator 28 flows through low pressure pipe 34 to the compressor 10, where the temperature of and pressure of the refrigerant vapor are raised as the vapor is compressed. The high pressure, hot vapor flows from the compressor though pipe line 12 to pressure regulating valve 36 which remains closed until the pressure developed in line 12 exceeds the opening pressure set for valve 36. The high pressure, hot vapor in line 12 is applied through equalizing line 38 tothe top of liquid receiver 20 and makes instantly available a supply of liquid refrigerant from the receiver 20 through line 26 to the expansion valve 30 or other metering device at not less than a predetermined pressure. When the refrigerant compressor 10 starts, the discharge pressure in line 12 almost at once rises to the opening pressure of regulating valve 36. A part of the compressed vapor flows through equalizing line 38 and valve 39. The contents of the receiver 20 are at once pressurized thus causing an immediate and full refrigerant liquid flow through expansion valve 30 or other equivalent metering device to the evaporator 28. The pressure on the surface S of the liquid R in the receiver also causes a rapid reverse fiow of liquid refrigerant R back through pipe 22 and into the condenser 14. As the liquid level in the condenser rises, the saturated condensing pressure in the condenser above the flooded portion rapidly rises to equal the pressure on the surface of the liquid in the receiver and to stop the liquid flow from the receiver. Then, the pressure in the condenser rises further due to incoming pressurized vapor from line section 12a to reverse the direction of liquid flow and the liquid in the bottom of the condenser returns to the receiver via line 22. The amount of liquid which returns to the receiver depends on ambient air temperature, temperature in the cooling chamber 32, and the quantity and pressure of vapor in the condenser. In the upper part of the condenser, condensation of the refrigerant vapor takes place at a pressure that varies with the volume and temperature of the cooling air being passed across or through the air-cooled condenser, and the condenser surface available, the condensed liquid refrigerant flows by pressure difference and/or by gravity to the bottom of the condenser and through connecting line 22 to the receiver.

If the ambient air temperature rises the internal condensing temperature-pressure rises. This increase in pressure returns more of the liquid refrigerant to the receiver to enlarge the available condensing surface of the condenser. Thus, a new dynamic balance is set. The dynamic pressure balance is quantitatively determined by the vapor pressure on surface S of liquid R in the receiver, plus the resistance to flow of the liquid condensate being returned to the receiver, plus the through circuit pressure drop in the condenser, and minus the liquid head H. The liquid head H is the difference between the liquid level S in the receiver and the operating level L in the condenser. This quantity is a dynamic value varying in response to the voiume or surface needed in the condenser for any particular operating condition. The system would be designed so that under full load conditions at high ambient temperature the full surface of the condenser is used and all the liquid passed from the receiver is returned to it.

Under certain conditions, valve 39 may be omitted, but then the equalizing line must be designed to perform an equivalent function. The line 38 will then have a fine or restricted bore of such size that pressure supplied through line 38 to receiver 28 is less than the full pressure supplied to line 12a via valve 36. Driving pressure will be maintained in the receiver at all times by passing a constant supply of pressurized refrigerant. Thus the evaporator 23 and expansion valve 39 will operate efficiently regardless of outside temperature. It will be understood that at low ambient temperatures, the level of liquid in the receiver will vary with the amount of liquid required to back-flood the condenser so that the condenser operates at maximum efficiency at all times.

To summarize the operation of the system, at low ambient temperatures, the level of liquid in the receiver will vary with the amount of liquid required to back-flood the condenser. The level of liquid in the condenser is maintained automatically so that minimum condensing pressure is maintained during low-ambient operation. The liquid received from the receiver will drain out the condenser entirely through line 22 when the compressor is stopped, and when the condenser and liquid receiver are at the same ambient temperature. Suitable piping and control techniques may be employed to compensate for offcycle conditions that may occur when the several high-side components are located in different ambients.

The refrigeration system S2 shown partially in FIG. 2 is substantially identical with system S1 and corresponding parts are identically numbered. In system S2 equalizer line section 38 has an extension 38a extended below the surface S of liquid refrigerant R and terminates in a horizontal distributor tube 85. This tube has apertures 86 for passing streams of refrigerant vapor into the body of liquid R. These vapor streams will have the effect of agitating the liquid to mix oil and liquid refrigerant components which may otherwise tend to separate. Furthermore these vapor streams will lose heat to the sub-cooled liquid R and flash-heat the liquid R by cooling and condensing. As liquid R is thus warmed, the saturated vapor pressure above liquid R in vapor space S will rise. The equalizer line extension 38a in receiver 20 will be provided with holes 88 inside of the vapor space S for passing part of the compressed hot refrigerant vapor thereto, while the remaining vapor passes out through the distributor tube 85.

It is understood that the physical construction of the sub-surface liquid covered distributor tube 85 with aperture 86 may include where the pressure characteristics of the refrigerant being used require it, expansion and/or pressure dropping items, such as extended small bore tubes, perforated plates, screens, bafiies and so forth or a combination of such items to limit the velocity of the hot gas being dispersed within the body of the liquid R. The total pressure on the top of the liquid R will thus be the sum of the saturated vapor pressure of the liquid R in the vapor space S plus the partial pressure of the vapor fraction admitted to the vapor space S through holes 88.

By suitable choice of the number and size of the orifice holes 88, and/or by locating holes 88 in a separate, valve controlled, hot gas distributor tube, differentially controlled by commercially available control valves, the reheat of the sub-cooled liquid R in the receiver may be limited and/ or closely controlled to provide a liquid supply to the expansion valve or other metering device S at a minimum maintained pressure and at a desired temperature. By controlled reheat it is possible to maintain specified sub-cooling of the liquid entering the expansion valve.

In system S1 there is some flash reheating of liquid R occurring at the interface S of the condensed liquid and hot vapor in the receiver. However the arrangement of system S2 will effect more positive and controlled reheating as indicated above.

It will be apparent that both systems described operate on the same basic principle of back-flooding the condenser to effect hydrodynamic balance therein at all times. This mode of operation contrasts with that of the system described in my prior patent above mentioned. In the prior system, the condenser was operated cyclically, so that some time was required for the condenser to accommodate to changing ambient conditions to operate at maximum efficiency. In the present invention, the response of the condenser is immediate and automatic at all temperatures. These improved results are obtained with a simplified arrangement of apparatus.

While I have illustrated and described the preferred embodiments of my invention it is to be understood that I do not limit myself to the precise construction herein disclosed and that various changes and modifications may be made within the scope of the invention as defined in the appended claims.

What is claimed is:

1. A refrigeration system, comprising the following members connected in a closed series circuit: a refrigerant vapor compressor, air-cooled condenser, refrigerant receiver, and liquid refrigerant evaporator and a refrigerant metering device; each of said members having an inlet and an outlet, said receiver comprising a closed container having a body of liquid refrigerant therein with a vapor space above the liquid in the receiver, a low pressure line connecting the outlet of the evaporator to the inlet of the compressor, a high pressure hot-gas line connecting the outlet of the compressor to the inlet of the condenser at an upper end thereof, a liquid conducting unobstructed first conduit connecting the outlet of the condenser at a lower other end thereof to an inlet of the receiver at the bottom of said body of liquid, a second liquid conducting conduit connected from the outlet of the receiver through the metering device to the inlet of the evaporator, said second conduit having an intake located below the surface of the liquid in the receiver, a first normally open pressure responsive valve located in said high pressure hot-gasline between the compressor and condenser when the pressure of refrigerant vapor applied to said valve is above a pre determined minimum pressure, and a pressure-equalizing pipe line connected at one end to a point of said high pressure line between said compressor and said first valve and connected at its other end into the receiver to pass pressurized hot vapor to the receiver, whereby the condenser is back-flooded by liquid from the receiver via said first conduit when vapor pressure in the condenser is less than liquid pressure applied through the first conduit from the receiver while the temperature of ambient air cooling the condenser is below a predetermined point and while the compressor is operating, whereby the evaporator is adequately supplied with liquid from the receiver at all times when the compressor is operating, regardless of the temperature of the ambient air, and whereby the receiver is supplied with liquid refrigerant from the condenser through the unobstructed first conduit due to a pressure head between the condenser and receiver When pressure in the condenser exceeds the vapor pressure at the surface of said liquid in the receiver.

2. A refrigeration system as recited in claim 1, wherein the equalizing pipe has a fine bore so that the pressure of refrigerant vapor passed to the receiver is less than the pressure of refrigerant vapor passed through the first valve to the condenser, whereby refrigerant liquid is driven from the receiver to the condenser immediately upon starting of the compressor as refrigerant vapor passes through the equalizing line and before the condenser passes any condensed refrigerant liquid to the receiver.

3. A refrigeration system as recited in claim 1, further comprising a normally open differential pressure responsive second valve located in said equalizing line to pass pressurized hot refrigerant vapor to the receiver at a pressure less than the pressure required to open the first valve, whereby refrigerant liquid is driven from the receiver to the evaporator when the compressor is started as refrigerant vapor passes through the equalizing line and before the condenser passes any condensed refrigerant liquid to the receiver.

4. A refrigeration system as recited in claim 1, wherein the equalizing line is extended inside the receiver and terminates below the surface of said liquid to discharge pressurized hot refrigerant vapor therein for agitating the liquid and flash heating the same, said equalizing line having lateral openings inside the receiver above the surface of the liquid therein to discharge the pressurized hot refrigerant vapor into the receiver in a vapor space above the surface of the liquid.

5. A refrigeration system as recited in claim 4, further comprising a distributor tube connected to the end of the equalizing line inside the receiver, said tube being disposed near the bottom of the receiver and being laterally apertured for distributing said vapor in fine streams a multiplicity of streams into the body of liquid in the receiver.

6. A refrigeration system as recited in claim 2, wherein said equalizing line is extended inside the receiver and terminates below the surface of said liquid to discharge pressurized hot refrigerant vapor therein for agitating the liquid and flash heating the same, said equalizing line having lateral openings inside the receiver above the surface of the liquid therein to discharge the pressurized hot refrigerant vapor into the receiver in a vapor space above the surface of the liquid.

7. A refrigeration system as recited in claim 6, further comprising a distributor tube connected to the end of the equalizing line inside the receiver, said tube being disposed near the bottom of the receiver and being laterally apertured for distributing said vapor in fine streams a multiplicity of streams into the body of liquid in the receiver.

8. A refrigeration system as recited in claim 3, wherein the equalizing line is extended inside the receiver and terminates below the surface of said liquid to discharge pres surized hot refrigerant vapor therein for agitating the liquid and flash heating the same, said equalizing line having lateral openings inside the receiver above the surface of the liquid therein to discharge the pressurized hot re frigerant vapor into the receiver in a vapor space above the surface of the liquid.

9. A refrigeration system as recited in claim 8, further comprising a distributor tube connected to the end of the equalizing line inside the receiver, said tube being disposed near the bottom of the receiver and being laterally apertured for distributing said vapor in fine streams a multiplicity of streams into the body of liquid in the receiver.

10. A refrigeration system as recited in claim 1, further comprising a distributor tube connected to the end of the equalizing line inside the receiver, said tube being disposed near the bottom of the receiver and being laterally apertured for distributing said vapor in fine streams a multiplieity of streams into the body of liquid in the receiver.

References Cited UNITED STATES PATENTS 2,933,904 4/ 1960 Wellman 62196 2,934,911 5/1960 Micai 62-117 2,963,877 12/1960 MalkOif 6 -196 3,149,475 9/1964 Gislasori 62197 MEYER PERLIN, Primary Examiner. 

